The argument -t 10 states that we want the test to run for only 10 seconds.

There are other options which you can play with like:

-d ==> Do a bidirectional test simultaneously
-u ==> use UDP rather than TCP

View the list of options by executing:

$ iperf --help

There's also a GUI wrapper written in Java for iperf available at http://code.google.com/p/xjperf/. It offers a nice GUI which allows you to choose different options to run iperf with and also displays output from iperf in a nice graph: